We analyze the performance of two common tag schemes: BIO (Begin, Inside, Outside) and BIOUL (BIO with Unary and Last tags) to encode observed (i.e., previously predicted entities). Results can be found in Table REF . The BIOUL tag scheme shows better overall results than the BIO scheme. This conclusion is similar to what others [1]} have observed for flat named entity recognition. However, the BIOUL "reading" tag scheme's better results show that the system can better use previous entities for its predictions when given begin and end bounds.
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